Plate clamp



3- F. J. BREMAN EIAL 2,309,161

PLATE CLAMP F May 25, 1939 Jan. 26, 1943.

F. J. BREMAN, EI'AL PLATE CLAMP 4 Sheets-Sheet 2 Filed May 25, 1939 d .p a mm Jan. 26, 1943. F. J. BREMAN ETAL 2,309,161

PLATE CLAMP Filed May 25, 1939 4 Sheets-Sheet 3 lfzu M JBPQW Edward ZDcad Jan. 26, 1943. J BREMAN ETAL 2,309,161

PLATE CLAMP Filed May 25, 1939 4 Sheets-Sheet 4 memes. 26, 1943 PLATE CLAMP Frank J. fireman, Oak Park, and Edward F. Dell,

Park Ridge, 111., assiznors to Davidson Manufacturing Corporation, a corporation of Il linois Application May 25, 1939, Serial No. 275,722

14 Claims. (Cl. 101-4151) In the art of fastening printing plates to the.

.desirable that the plate be located and held in register with as few operations and adjustments as possible and that this registry be maintained under all running conditions without the slightest variation.

The present invention provides a plate clamp which clamps the plate at each end in a single operation with a uniform clamping pressure distributed at spaced points along the ends of the plate by a construction that will not yield to let the plate move out of register during operation of the press.

An even and uniform draw is imposed by the clamp of the present invention upon the plate over the entire area thereof along the leading and back edges and all stretch or looseness due to initial slackness or creep arising under running conditions is removed automatically without any need for stopping the press to make special adjustments.

Moreover, the clamping mechanism, provided by the invention, can be used with most, if not all, of the plates of conventional construction without injuring them or rendering them unfit for storage or regraining and re-use upon other machines which might have different kinds of clamps.

In addition to the fact that the plate is not injured by the clamping means, it is also important that the plate need not be perforated to be held firmly in place and adjustment for alignment, and side registry can be made with great rapidity without refolding or repunching the plate as is the case with many conventional clamps.

The present invention further provides an improved clamping mechanism which is simple in construction, easily manufactured, assembled and operated and can be adjusted and kept in adjustment with a minimum amount of attention throughout long periods of operation.

These being among the objects of the invention, other and further objects will appear from the drawings, the description relating thereto and the appended claims.

Referring now to the drawings:

Fig. l is a section through a portion of a plate drum, taken transversely to the axis of rotation thereof and illustrating a preferred embodiment of the invention;

Fig. 2 is a view taken on the line 2-2 in Fig. 1

showing the construction of the clamping unit for the leading edge of the plate;

Fig. 3 is a view taken on the line 3-3 in Fig. 1, showing the clamping unit for the back edge of the plate;

Fig. 4 is similar to Fig. 1, showing compositely the:l gections taken upon lines l4 in Figs. 2 an Fig. 5 is a top perspective of a plate as used with the preferred embodiment;

Fig. 6 is a perspective of the adjusting means employed to place the clamping members in perfect alignment to provide uniform gripping pressure throughout;

Fig. 7 is a section taken transversely through a plate cylinder and associated blanket drum to illustrate another embodiment of the invention;

Fig. 8 is a top plan view from outside of the plate cylinder shown in Fig. 7, looking into the ap;

Fig. 9 is a section taken on the line 9-9 in Fig. 8;

Fig. 10 is a section taken on the line ill-l0 inFig.8;

Fig. 11 is an exploded perspective view of the clamp shown in Fig. '7 employed to hold the back edge of the plate;

Fig. 12 is a view'similar to Fig. 8 showing another embodiment of the invention;

I Fig. 13 is a section taken on the line l3--l3 in Fig. 12;

Fig. 14 is a perspective of a plate for use with either of the last two illustrated embodiments;

Fig. 15 is a section similar to Fig. 1 illustrating another form of the invention;

Figs. 16 and 17 are sections taken upon lines lB-I6 and !'l--I1 respectively in Fig. 15;

Fig. 18 is a section taken on the line l8--|O in Fig. 16; and

Fig. 19 is a section taken on the line |9-l9 in Fig. 16.

Referring now to Fig. 1, a plate drum 20 is illustrated as equipped with the preferred embodiment of the invention. The drum 20 revolves in the direction of the arrow and il provided with a gap 2! bounded by two radial shoulders 22 and 23. Slightly rounded leading and trailing edges 26 and 21 are provided where the shoulders 22 and 23, respectively, join the printing surface 24.

Within the gap.2l, two cooperating clamping umts are mounted. These units will be referred to as the leading unit 28, located at the leading edge 26 and the trailing unit 29 located at the trailing edge 21. Many of the parts used in the construction of these two units are identical for the purpose of attaining manufacturing and inventory economies, and may be considered interchangeable bctween units, it being understood that, to-this extent, like numerals refer to the like parts.

Referring briefly to Fig. 5, an offset printing plate 36 is illustrated ready for mounting upon the drum 26. The plate 30 may be made of zinc or aluminum, grained and treated for printing with the edge 3| designed to be the leading edge and the other edge 32 the trailing edge. Although both edges may be shaped and fashioned in various ways for different clamps, they are preferably square cut and flat, as shown for the present invention, even though the clamping means about to be described, will work with any disposed with the inner face 4| thereof in a plane slightly chordal to the periphery of the drum 26 and the side 40 is radially within the confines of the surface of revolution defined by the cylindrical face 24 of the drum so that the inking rollers (not shown) may be cleared. The side 46 is tapered as at 46a to facilitate insertion of the plate 30 below the face 4| which can. be accomplished readily without creasing or bending the plate.

The otherside 42 of the angle member is for strengthening of the side 40 against radial movement of the latter under strain and stress,.the ends of the side 40 being supported likewise by the end plates 33 and 34. The side 42 is slotted as at 43 to receive a handle 44 and notched as at 45 to support springs 46 and 41, the handle and springs and their function being described at greater length a little later.

A stifl cylindrical shaft 56 is mounted eccentrically on the axis 5| thereof to rotate about an axis 52 spaced from the inner face 4| of the angle member 35 a distance appreciably less than the largest radius of the off-center rotation of the cylindrical shaft so that there is provided between the cylindrical surface 53 of the shaft and the face 4| of the angle member 35 a progressive camming relation upon rotation of the shaft This camming relation inabout the axis 52. creases and tightens as the outer periphery of the shaft 50 is rotated towards the leading edge At one end, 54, the shaft 50 is mounted in the end plate 33 by a pin and journal construction 55 whose axis of rotation coincides with and determines the axis 52 for that end of the shaft.-

At the other end 56 an adjustment is provided which varies the axis 52 to locate it so that pressure between the shaft and the side 46 of the angle member is uniform throughout the length thereof.

This adjustment comprises a crank pin 51 (Fig.

' 6) with a long shank 6|! rotatably received in a longitudinal bore 6| in the shaft 56 where it is adjustably secured against relative rotation and longitudinal displacement by the set screw 62.

the trailing edge 21.

An intermediate crank portion 63 abuts against the end plate 34 and carries, on the opposite side and off-center the first pin 51, a second crank pin 64 which is received in a bore 65 through the end plate 36. The length of the pin. 64 is approximately the thickness of the end plate and is kerfed as at 66 to receive a screwdriver for adjusting purposes. The end wall 36 of the drum is cut away as at 61, to permit access to the pin 64.

In mounting the shaft 50 in place, the set screw 62 is loosened and the crank portion 63 and pin are collapsed in the bore 6|. The pin 55 is inserted, the shaft raised to position, the crank portion 63 expanded against the end plate 34 with the pin 64 entering the hole 65 and the set. screw 62 is retightened after the pressure between the side 40 of the angle member and the shaft has been equalized throughout.

As will be seen in Figs. 2 and 3, the shaft 56 has segments cut from the periphery thereof along the side next to the face 4| whereby spaced cylindrical areas 10 of preferably equal longitudinal lengths are provided at spaced points to allocate the clamping pressure exerted by the shaft to predetermined areas. In this way the spacing of the clamping areas 10, and their size not only may be so constructed and arranged to provide a clamping pressure which is uniform throughout the length thereof, but the total poundage pressure exertable by the clamping shaft is distributed or concentrated to limited areas so that at each point the poundage per square inch is greatly increased.

The clamping relation is released by depressing the handle 44 inwardly. This rotates the clamping areas away from the leading edge 26 to release the pressure against the side 46. The clamping relation is increased by the tension spring 46 which interconnects an arm 1| on the shaft and the side 42 in a manner rotating the clamping areas into engagement with the face 4|.

The trailing unit 29 is practically identical in construction with the leading unit 28 except that the end plate 12 extend radially inwardly a greater distance and are mounted by hearing bolts 13 to pivot about an axis 14 located intermediate the shaft 50 and the axis of the drum 20. A tension spring 41 moves the shaft 50 angle member 40 while the other hand depresses.

the handle 44. A spacer 15 of any predetermined width locates the leading edge 3|, and

when thus located, the handle 44 is released. A slight pull may then be made to seat the gripper firmly.

The drum 23 is then rotated and the plate 30 is wrapped around the drum until the trailing edge 32 of the plate overlaps the trailing edge 21 of the drum. At this time the spring 41 will be holding the trailing unit 23 away from The trailing edge 32 is then pushed inwardly until it is aligned to go between the shaft 50 and-the face 4| of the angle member of the trailing unit 23. The handle 44 thereof is then depressed by one hand inwardly and toward the trailing edge 21 while the other 1 hand directs the trailing edge into place. The trailing unit 23 is brought against the shoulder 23 and the handle 44 is released; The plate 36 is gripped and a slight pull upon the handle set the grip to be maintained by the spring 48. The spring 41 comes into immediate operation to take up the slack and creep present or developing in the plate. In this way with practically a single movement for each clamp, the plate can be mounted in perfect registry on the drum or released for removal.

Not only this, but with this embodiment of the clamp,the plate is kept straight and need not be bent for use and unbent for regraining or storage.

With reference to the texture 'or finishes of the faces 4| and the cylindrical surfaces 10, it

the plate 18 over the trailing edge 21 is unnecessary to take up slackness developing when the plate is being run in. This feature, taken in conjunction with the automatic slack takeup provided by the spring 41a, obviates the danger of a loose fold or buckling arising at the trailing edge of the plate which is present with the con- I ventional clamps where the printing machine has is preferable that the faces 41 be unpolished or moderately roughened and the cylindrical surface 10 be moderately polished. With this arrangement the plate tends to adhere immovably to the faces u. The pull on the plate tends to rotate the cylinder to develop a tightening move ment'of the cylinder without slippage. Register is thereby maintained. Moreover, the mechanical area of clamping pressure is appreciably larger between the fiat faces 4| and the plate than between the round cylindrical surfaces of the shaft which tangentially engage the plate. Although this is a lesser factor with thinner plates, it is significant where the plate is quite thin and backed by a fibrous layer of material which might cause slippage. In fact, fiber backed plates can be used with the clamp of the present invention with much less danger of injury than with conventional clamps.

Thus, the clamping pressure developed by the present invention increases with the pull upon the plate as the need therefor arises and the plate may be readily released by the movement of a single handle for each clamp unit. Moreover, any creep or initial slackness of the plate which appears after the drum has been run awhile is automatically removed as it develops and the plate is subjected, at all times, to an even and uniform stretch throughout.

In view of the fact that the cylindrical sections 10 are at. spaced points some localized stretching of the plate will exist. Although this is true with any clamp it is a great deal less with the embodiment of the invention described. The double reverse, slight bend at each end of the plate which is induced by the edges 28 and 21 and the relative location of the sides 4|, provide a slight snubbing action which keeps the working portion of the plate 30 entirely free from any signs whatsoever of pull or draw lines due to clamping or tension.

Referring now to Figs. 7-11, the embodiment illustrated there has the angle member of the trailing unit 29a rotated through an angle of 180 and the face 4la is radially disposed approximately parallel with the shoulder 23 while the leading clamping shaft 50 works directly against the shoulder 22. The spring supports are altered correspondingly wherein the leading unit spring 45a and the spring 41a are secured at one end directly to the drum. Otherwise the operation of the clamping units are the same except that the operation of the handles 44 are different moving outwardly for release and inwardly for clamping.

In this embodiment, more access is provided in the gap, for any given size thereof, and the drum is used with a bent plate such as that indicated by the numeral I8 in Fig. 14 where the leading edge TI is bent as at 18. I With this particular embodiment of the invention a rebending of the trailing'edge 18 of may be used for repeat runs of plates originally.

bent and used upon other equipment. The automatic plate take-up of the invention tolerates this and is a feature which broadens the application and use of particular plates in different offset printing presses.

Referring now to Figs. 12 and 13, a modification of the structure shown in Fig. 7 is illustrated wherein the resilient means is'employed for securing the bent edges of the plate in place. shepherds crook spring members are secured to the transverse rod 8| by screws 82 so that the free edge 83 of the spring presses against the face Mb. The rod BI is supported at both ends upon the trailing unit 29b by a journal 84 at one end and a journalled sliding pin 85 at the other end. A torsion spring 88 resiliently urges rotation of the rod 8| in a direction whereby the free end 83 of the spring 80 is pressed into clamping relationship with the bent end 19 of the plate. A handle 81 is employed to overcome the pressure of the torsion spring 86 to release the clamping pressure exerted by the free ends 83 of the shepherds crook spring 80. The clamping relation of the leading edge 22 of the drum is positively applied by means of a rocker arm and a held in place by the heavy spring pressure exerted directly against the ends of the plate whereby a snubbing action around the leading and trailing edges operates to prevent the bent end of the plate from slipping out of registry.

The shepherds crook springs are located at spaced intervals and because of the individual and independent resiliency of each one, a sufficiently even and uniform clamping pressure is exerted by each without any need for adjusting the axial alinement of the supporting shafts 8| and 9|. This particular embodiment is less expensive to manufacture and if, at any time, any one of the springs 88 is injuredor broken they can be replaced with little trouble since the screws 82 are accessible for removal and replacement of the springs 80 when the shafts 8i and iii are rotated to their non-clamping position.

In Figs. 15 to 19 inclusive, a modification of the integral cam construction heretofore described is shown as constructed of a plurality of elements. In this embodiment, individual cams I00 comprising eccentric wheels are substituted In mounting the cams upon the shaft, the a shaft IOI is provided with longitudinally aligned radial bores I03 located at spaced intervals throughout its length. The cams are provided with slots I04 located slightly to one. side of their greatest radius, and pegs I05 are driven into the bores I03 through the slots I04 to hold the cams axially and rotatively in place.

An intermediate peg I06 extends beyond the periphery of its cam and through the slot 43 to serve as a handle for rotating the shaft lI whereby all pegs I function as a unit to rotate the cams I00. The relative sizes of the peg and slots are such that enough clearance is provided to have a loose connection at these points which takes care of any manufacturing irregularities in the construction of the cams and any give that might exist in the shaft I 0| when the shaft bears the strain of the clamping pressure.

The cams I00 are normally urged into clamping engagement by means of spring I01, preferably one spring for each cam. The springs interconnect the side 42 of the L member 35 and projections I08 carried by the cams. In this way each cam is tensioned independently of the others, yet is permitted enough relative movement by the loose connection of the pegs I04 to maintain independently of each other a uniform clamping pressure upon the plate.

During rotation of the cylinder in the printing operation, the pegs ride toward the outer shoulder of the slot 03 under the action of centrifugal force in a manner favorably affecting the cam pressure as induced by the springs i 01. Then when the plate 30 is to be removed the arms I06 are forced inwardly with the pegs I05 engaging the inner shoulder IIO of the cams to overcome the springs I01 and rotate them out of their clamping position.

In assembling this particular embodiment, the cams I00 are first located upon the shaft l0l after which the pegs I05 are driven into bores I03 upon the shaft at predetermined points. The shaft is then inserted into the respective L-member and the trunnions I02 threaded into the ends of the shaft through the end plates 33 and 12. The springs I01 are mounted and the assemblage is inserted into the gap of the cylinder and fastened into place by bolts 31 and 13, as already described.

Consequently, although several embodiments of the invention have been shown and described herein, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the invention, the scope of which is commensurate with. the appended claims.

What is claimed is:

1. The combination of a plate drum having a gap, plate clamping elements mounted in the gap for relative movement about spaced axes including cooperating members rotatably mounted with respect to each other about a relatively fixed axis and in frictional contact with the plate, means fixating one of the clamping elements relative to the drum, and resilient means connected to one of the elements for exerting a plate tensioning movement relative to each other to take up slack int-he plate automatically during printing operations.

2. A plate mounting comprising identical circumferentially spaced and relatively movable clamping devices including pairs of mutually cooperating elements eccentrically mounted with respect to each other, resilient means for establishing and maintaining a clamping of the plate between said elements, means for relieving said clamping when the mutually cooperating elements are moved in one direction and for assisting said elements to establish a clamping relation when moved in the opposite direction, and resilient means for urging the devices circumferentially to reduce said space to stretch the plate under a continuous resilient force in a manner also assisting the first resilient means.

3. A mounting for a printing plate comprising parallel shoulders facing each other, spring members having substantially identical shape characteristics mounted adjacent the shoulders for movement about axes spaced from the shoulders a distance less than their extended radii, resilient means urging engagement between the members and the respective shoulders and means urging said shoulders towards each other relatively.

4. A mounting for a printing plate and including a member having one edge of the plate secured thereto, spring-tightening means engaging the plate at spaced points, and resilient means urging the first means towards said member in an arc whose center is within the circle transcribed by the plate in printing operation. 5. In a plate clamping element, a, shoulder, a shaft, a plurality of cams disposed at intervals longitudinally along the shaft for cooperation with the shoulder over spaced restricted areas thereof, and means carried by the shaft for manually operating the cams in unison to rotate them and relieve the contact between cams and the shoulder to receive the plate therebetween.

6. A mounting for a printing plate comprising two elements having shoulders spaced from and movable relative to each other, a shaft jourrialled in each of said elements with the axes thereof parallel to the respective shoulders, cams mounted upon each shaft with the greatest radius thereof appreciably larger than the distance between the shoulders and the axes of the respective shafts, means for rotating the shaft, loose connection means between the shaft and the cams for rotating the cams relative to the shoulder, and resilient means rotatably urging each cam individually into contact with said shoulder.

7. A clamp for holding a flexible printing element in place upon a printing cylinder comprising a plurality of cooperating clamping devices, one of which receives an end of the element in registered position and includes eccentric means adapted to clamp the end in place when rotated in one direction and to release said end when rotated in another direction, a second device.

operative clamping devices cooperating with each other to stretch the printing element upon the printing cylinder, oneof saiddevices receiving an end of the element in end-registered position, including a rotatably mounted bar, self-tightening means upon the bar rotatable about an eccentric axis, means for adjusting the alignment of the self-tightening means, means for rotating the bar to move said self-tightening means into and out of clamping position, a second clamping device including an eccentrically operative member for clamping the other end of said element.

9. In a printing press having a gap in a printing cylinder, a plate clamp comprising a plurality of mutually cooperating elements mounted for relative movement in the gap to engage independently the ends of a plate and including a structurally reenforced anvil member, removable bearing studs mounted thereon, rotatable means having a cylindrical surface mounted eccentrically with respect to the studs, means for rotating said rotatable means into and out of engagement with the anvil, means including one of the studs for aligning said rotatable means with the anvil, and resilient means normally urging rotation of the rotatable means into contact with the anvil for holding the plate in clamping position.

10. In a plate clamp for a printing press, an anvil, a shaft, a plurality of cams disposed at intervals longitudinally along the shaft. rotatable with respect thereto and adapted to cooperate with the anvil over spaced restricted areas thereof, resilient means adapted to actuate each cam independently into clamping relationship with the anvil, and means carried by the shaft and operable with one hand for rotating all of the cams in a clamp opening direction to receive or release a plate therein.

11. A plate drum for a printing press, having a cylindrical surface interrupted to form a gap therein, means near one end of the gap for securing the leading edge of a plate in fixed relationship to the drum, and a clamp near the other end of the gap for clamping the trailing edge of the plate movable and resiliently urged in a direction to stretch a plate extending around the drum and including an anvil, a shaft, a plurality of cams disposed at intervals longitudinally along the shaft, rotatable with respect thereto and adapted to cooperate with the anvil over spaced restricted areas thereof, resilient means adapted to actuate each cam independently into clamping relationship with the anvil, and means carried by the shaft and operable with one hand for rotating all of the cams in a clamp opening direction to receive or release a plate therein and for moving the clamp in a direction opposite to the plate stretching direction.

12. A plate drum for a printing press, having a cylindrical surface interrupted to form a gap therein, means near one end of the gap for securing the leading edge of a plate in fixed relationship to the drum, and a clamp near the other end of the gap for clamping thetrailing edge of the plate movable and resiliently urged in a direction to stretch a plate extending around the drum and including an anvil, a plurality of rotatable grippers disposed at intervals longitudinally along the anvil and adapted to cooperate with the anvil over spaced restricted areas thereof, resilient means adapted to actuate each gripper independently into clamping relationship with the anvil, and means operable with one hand and in one stroke for rotating all of the grippers in a clamp opening direction to receive or release a plate therein and for moving the clamp in a direction opposite to the plate stretching direction.

13. A plate drum for a printing press, having a cylindrical surface interrupted to form a gap therein, means near one end of the gap for securing the leading edge of a plate in fixed relationship to the drum, and a clamp near the other end of the gap for clamping the trailing edge of the: plate movable and resiliently urged in a direction to stretch a plate extending around the drum, and means operable with one hand and in one stroke for opening the clamp to receive or release a plate therein and for moving the clamp in a direction opposite to the plate stretching direction.

14. A plate drum for a printing press, having a cylindrica1 surface interrupted to form a gap therein, means near one end of the gap for securing the leading edge of a plate in fixed relationship to the drum, and a clamp near the other end of the gap for clamping the trailing edge of the plate movable and resiliently urged in a direction to stretch a plate extending around the a drum, and movable with one hand in the opposite direction, and means readily operable with the same hand at the same time for opening the FRANK J. BREMAN. EDWARD F. DELL. 

